Process for controlled radical polymerization in aqueous dispersion

ABSTRACT

The present invention relates to a process for controlled radicalpolymerization in aqueous dispersion in the presence of selected nitroxyl radicals having a defined partition equilibrium between water and monomer as measured by their log p. wherein p is the partition coefficient of the nitroxyl radical in octanol and water.

[0001] The present invention relates to a process for controlled radicalpolymerization in aqueous dispersion in the presence of selectednitroxyl radicals having a defined partition equilibrium between waterand monomer as measured by their log p, wherein p is the partitioncoefficient of the nitroxyl radical in octanol and water.

[0002] Polymerization processes using water as a continuous dispersingphase wherein initially the monomers and after polymerization thepolymers are dispersed are widely used for manufacturing polymers(aqueous dispersion polymerization). Mostly, water and a water-insolublemonomer, an emulgator and/or a protective colloid and a suitableinitiator system are mixed by generally known methods building a monomerswollen micellar system or stabilized monomer droplets.

[0003] Of particular interest are emulsion polymerizations, whereinusually water soluble initiator systems are used.

[0004] The monomers are essentially insoluble in the aqueous phase andform finely distributed droplets therein. The addition of dispersingagents such as for example sodium dodecyl-sulfate is in many casesnecessary to achieve such stable droplets and micelles. Examples ofdispersing agents are for example given in “Ullmann Enzyklopädie dertechnischen Chemie, Bd.10, 4. Auflage, Verlag Chemie, Weinheim (1975),page 449”.

[0005] Several variations are known in the state of the art, for exampleemulgator free emulsion polymerization, mini emulsion polymerization andmicro emulsion polymerization. These variations are characterized bychanges of kind and amount of the emulgator and initiator systemsleading to different polymer products especially with regard tomolecular weight, polymer particle size and their distributions.

[0006] Polymers or copolymers prepared by free radical polymerizationprocesses inherently have broad molecular weight distributions orpolydispersities which are generally higher than about four. One reasonfor this is that most of the free radical initiators have half livesthat are relatively long, ranging from several minutes to many hours,and thus the polymeric chains are not all initiated at the same time andthe initiators provide growing chains of various lengths at any timeduring the polymerization process. Another reason is that thepropagating chains in a free radical process can react with each otherin processes known as combination and disproportionation, both of whichare irreversibly chain-terminating reaction processes. In doing so,chains of varying lengths are terminated at different times during thereaction process, resulting in resins consisting of polymeric chainswhich vary widely in length from very small to very large and which thushave broad polydispersities. If a free radical polymerization process isto be used for producing narrow molecular weight distributions, then allpolymer chains must be initiated at about the same time and terminationof the growing polymer-chains by combination or disproportionationprocesses must be avoided.

[0007] A method to reduce polydispersity and to avoid the disadvantagesof conventional radical polymerization has already been described bySolomon et al., U.S. Pat. No. 4,581,429, issued Apr. 8, 1986, wherein afree radical polymerization process is disclosed which controls thegrowth of polymer chains to produce short chain or oligomerichomopolymers and copolymers, including block and graft copolymers. Theprocess employs an initiator having the formula (in part) R′R″N—O—X,where X is a free radical species capable of polymerizing unsaturatedmonomers. The reactions typically have low conversion rates.Specifically mentioned radical R′R″N—Oe groups are derived from 1,1,3,3tetraethylisoindoline, 1,1,3,3 tetrapropylisoindoline, 2,2,6,6tetramethylpiperidine, 2,2,5,5 tetramethylpyrrolidine or dij-butylamine.

[0008] In WO 99100426 emulsion polymerization of ethylenicallyunsaturated monomers in the presence of nitroxyl radicals has beendescribed in greater detail, pointing out that the monomer droplets havea size of less or equal 500 nm.

[0009] Recently in EP 970973 emulsion polymerization in the presence ofa stable free radical has been described, pointing out that the watersolubility of the stable free radical is at least 0.1 g/l at 25° C.Additionally, in WO 99/11674 the requirement of the molale solubility ofthe nitroxyl radicals in the aqueous medium is described as being atleast 10⁻⁶ mol/kg and most preferred at least 10⁻¹ mol/kg at 25° C. and1 bar.

[0010] In the instant invention it has been found, that the mostimportant property of the nitroxyl radicals is not the good solubilityin water but the partition equilibrium between water and monomer asreflected by the log p value of the nitroxyl. The right balance betweensolubility in water and solubility in the monomer droplets influencesstrongly the efficiency in terms of polydispersity, rate ofpolymerization and yield.

[0011] The partition coefficient log p (octanol/water) is a widely usedparameter for example in rating the environmental impact of chemicalcompounds. Its calculation is described by W. M. Meylan, P. H. Howard inJ. Pharmaceutical Sciences 84, (1995), 83-92.

[0012] One subject of the instant invention is a process for preparingan oligomer, a cooligomer, a polymer or a copolymer (block or random) byfree radical polymerization in aqueous dispersion of at least oneethylenically unsaturated monomer or oligomer, which comprises formingan aqueous dispersion, having the monomer in the disperse phase and(co)polymerizing the monomer or monomers/oligomers at elevatedtemperature in the presence of

[0013] a) at least one stable free nitroxyl radical which has a log p(octanol/water) of between −0.5 and 7.5 and which is selected from thegroup consisting of a compound of formula (A), (B), (C), (D), (E), (F),(G), (H) or (I)

[0014] wherein

[0015] R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interruptedby one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalentradical of an aliphatic carboxylic-acid having 2 to 18 carbon atoms, ofa cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or anα,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of anaromatic carboxylic acid having 7 to 15 carbon atoms;

[0016] R₁₀₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl,C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl;

[0017] R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstitutedor substituted by a cyano, carbonyl or carbamide group, or is glycidyl,a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Zwherein Z is hydrogen, methyl or phenyl;

[0018] G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, and

[0019] G₁ and G₃ are methyl and G₂ and G₄ are ethyl or propyl or G₁ andG₂ are methyl and G₃ and G₄ are ethyl or propyl;

[0020] R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₆alkenyl, C₃-C₁₈alkinylwhich are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkylwhich is interrupted by at least one O atom and/or NR₅ group,C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R₄ togetherwith the linking carbon atom form a C₃-C₁₂cycloalkyl radical;

[0021] R₅, R₆ and R₇ independently are hydrogen, C₁-C₁₈alkyl orC₆-C₁₀aryl;

[0022] R₈ is hydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl;

[0023] C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substitutedby one or more OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which isinterrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl orC₆-C₁₀aryl, C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl,—O—C₁-C₁₈alkyl or —COOC₁-C₁₈alkyl; and

[0024] R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenyl orC₁-C₁₈alkyl; and

[0025] b) a free radical initiator.

[0026] The alkyl radicals in the various substituents may be linear orbranched. Examples of alkyl containing 1 to 18 carbon atoms are methyl,ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl,2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.

[0027] Alkenyl with 3 to 18 carbon atoms is a linear or branched radicalas for example propenyl, 2-butenyl, 3-butenyl, isobutenyl,n-2,4pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl,iso-dodecenyl, oleyl, n-2-octadecenyl oder n4-octadecenyl. Preferred isalkenyl with 3 bis 12, particularly preferred with 3 to 6 carbon atoms.

[0028] Alkinyl with 3 to 18 is a linear or branched radical as forexample propinyl —CH₂—C≡CH), 2-butinyl, 3butinyl, n-2-octinyl, odern-2-octadecinyl. Preferred is alkinyl with 3 to 12, particularlypreferred with 3 to 6 carbon atoms.

[0029] Examples for hydroxy substituted alkyl are hydroxy propyl,hydroxy butyl or hydroxy hexyl.

[0030] Examples for halogen substituted alkyl are dichloropropyl,monobromobutyl or trichlorohexyl.

[0031] C₂-C₁₈alkyl interrupted by at least one O atom is for example—CH₂—CH₂—O—CH₂CH₃, —CH₂—CH₂—O—CH₃— or —CH₂—CH₂—O—CH₂−CH₂—CH₂—O—CH₂—CH₃—.It is preferably derived from polyethlene glycol. A general descriptionis —((CH₂)_(a)—O)_(b)—H/CH₃, wherein a is a number from 1 to 6 and b isa number from 2 to 10.

[0032] C₂-C₁₈alkyl interrupted by at least one NR₅ group may begenerally described as —((CH₂)_(a)—NR₅)_(b)—H/CH₃, wherein a, b and R₅are as defined above.

[0033] C₃-C₁₂cycloalkyl is typically, cyclopropyl, cyclopentyl,methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl ortrimethylcyclohexyl.

[0034] C₆-C₁₀ aryl is for example phenyl or naphthyl, but also comprisedare C₁-C₄alkyl substituted phenyl, C₁-C₄alkoxy substituted phenyl,hydroxy, halogen or nitro substituted phenyl. Examples for alkylsubstituted phenyl are ethylbenzene, toluene, xylene and its isomers,mesitylene or isopropylbenzene. Halogen substituted phenyl is forexample dichlorobenzene or bromotoluene.

[0035] Alkoxy substituents are typically methoxy, ethoxy, propoxy orbutoxy and their corresponding isomers.

[0036] C₇-C₉phenylalkyl is benzyl, phenylethyl or phenylpropyl.

[0037] C₅-C₁₀heteroaryl is for example pyrrol, pyrazol, imidazol, 2, 4,dimethylpyrrol, 1-methylpyrrol, thiophene, furane, furfural, indol,cumarone, oxazol, thiazol, isoxazol, isothiazol, triazol, pyridine,α-picoline, pyridazine, pyrazine or pyrimidine.

[0038] If R is a monovalent radical of a carboxylic acid, it is, forexample, an acetyl, propionyl, butyryl, valeroyl, caproyl, stearoyl,lauroyl, acryloyl, methacryloyl, benzoyl, cinnamoyl orβ-(3,5-di-tert-butylhydroxyphenyl)propionyl radical.

[0039] C₁-C₁₈alkanoyl is for example, formyl, propionyl, butyryl,octanoyl, dodecanoyl but preferably acetyl and C₃-C₅alkenoyl is inparticular acryloyl.

[0040] The above compounds and their preparation are described in GB2335190 and in GB 2342649.

[0041] Preferred is a process, wherein in formula A, B and C

[0042] R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, amonovalent radical of an aliphatic, carboxylic acid;

[0043] R₁₀₁, is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoylor benzoyl;

[0044] R₁₀₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula—CH₂CH(OH)—Z or of the formula —CO—Z, wherein Z is hydrogen, methyl orphenyl.

[0045] Another preferred process is, wherein in formula (D), (E), (F),(G), (H) and (I) at least two of R₁, R₂, R₃ and R₄ are ethyl, propyl orbutyl and the remaining are methyl; or

[0046] R₁ and R₂ or R₃ and R₄ together with the linking carbon atom forma C₅-C₆cycloalkyl radical and one remaining substituents is ethyl,propyl or butyl.

[0047] Specific particularly suitable compounds are given in thefollowing Table. Compound No. Nitroxyl-Radical log p 101

2.6 102

3.0 103

2.2 104

7.4 105

5.9 106

4.9 107

4.0 108

3.5 109

2.4 110

5.1 111

4.6 112

1.5 113

6.8 114

4.9 115

5.6 116

4.6 117

2.0 118

6.8 119

5.8 120

4.9 121

3.9 122

1.9 123

3.6 124

3.1

[0048] Preferably log p is from 0 to 5 and more preferably from 1 to 5.

[0049] Preferably the free radical initiator of component b) is abis-azo compound, a peroxide or a hydroperoxide.

[0050] Specific preferred radical sources are2,2′-azobisisobutyronitrile,2,2′-azobis(2-methyl-2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),1,1′-azobis(1-cyclohexanecarbonitrile), 2,2′-azobis(isobutyramide)dihydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile,dimethyl-2,2′-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile,2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane),2,2′-azobis(N,N′-dimethyleneisobutyramidine), free base orhydrochloride, 2,2′-azobis(2-amidinopropane), free base orhydrochloride,2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide; acetyl cyclohexanesulphonyl peroxide, diisopropyl peroxy dicarbonate, t-amylpemeodecanoate, t-butyl pemeodecanoate, t-butyl perpivalate,t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoylperoxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide,bis (2-methylbenzoyl) peroxide, disuccinic acid peroxide, diacetylperoxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate,bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butylpermaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate,t-butyl perisononaoate, 2,5-dimethylhexane 2,5dibenzoate, t-butylperacetate, t-amyl perbenzoate, t-butyl perbenzoate, 2,2-bis(t-butylperoxy) butane, 2,2 bis (t-butylperoxy) propane, dicumylperoxide, 2,5dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy3-phenylphthalide, di-t-amyl peroxide, α,α′-bis(t-butylperoxy isopropyl)benzene, 3,5-bis (t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butylperoxide, 2,5-dimethylhexyne-2,5-di-t-butylperoxide,3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthanehydroperoxide, pinane hydroperoxide, diisopropylbenzenemono-α-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.

[0051] The radical initiator has preferably a water solubility of atleast 1 g/l at 20° C.

[0052] Most preferred are the following compounds, which are allcommercially available. WAKO VA-061

WAKO V-501

WAKO V-30

WAKO VA-086

WAKO VA-044

WAKO V-50

Natrium-peroxodisulfat Kalium-peroxodisulfat Ammonium-peroxodisulfat

[0053] It is also possible to use combinations of Fe-compounds orCo-compounds with peroxo salts or salts of bisulfites or hydrosulfites.These combinations are known as redox systems.

[0054] Preferably the ethylenically unsaturated monomer is selected fromthe group consisting of styrene, substituted styrene, conjugated dienes,acrolein, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleicanhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic esters,(meth)acrylonitriles, (alkyl)acrylamides.

[0055] More preferred the ethylenically unsaturated monomer is anacrylic acid ester, acrylamide, acryinitrile, methacrylic acid ester,methacrylamide, methacrylnitrile.

[0056] A preferred ethylenically unsaturated monomer conforms to formulaCH₂═C(R_(a))—(C═Z)—R_(b), wherein R_(a) is hydrogen or C₁-C₄alkyl, R_(b)is NH₂, glycidyl, unsubstituted C₁-C₁₈alkoxy, C₂-C₁₀₀alkoxy interruptedby at least one N and/or O atom, or hydroxy-substituted C₁-C₁₈alkoxy,unsubstituted C₁-C₁₈alkylamino, di(C₁-C₁₈alkyl)amino,hydroxy-substituted C₁-C₁₈alkylamino or hydroxy-substituteddi(C₁-C₁₈alkyl)amino or —O—CH₂—CH₂—N(CH₃)₂;

[0057] Z is oxygen or sulfur.

[0058] Examples for R_(b) as C₂-C₁₀₀alkoxy interrupted by at least one Oatom are of formula

[0059] wherein R_(c) is C₁-C₂₅alkyl, phenyl or phenyl substituted byC₁-C₁₈alkyl, Rd is hydrogen or methyl and v is a number from 1 to 50.These monomers are for example derived from non ionic surfactants byacrylation of the corresponding alkoxylated alcohols or phenols. Therepeating units may be derived from ethylene oxide, propylene oxide ormixtures of both.

[0060] Further examples of suitable acrylate or methacrylate monomersare given below.

[0061] Further acrylate monomers are No N

[0062] Examples for suitable monomers other than acrylates are

[0063] Preferably R_(a) is hydrogen or methyl, R_(b) is NH₂, gycidyl,unsubstituted or with hydroxy substituted C₁-C₄alkoxy, unsubstitutedC₁-C₄alkylamino, di(C₁-C₄alkyl)amino, hydroxy-substitutedC₁-C₄alkylamino or hydroxy-substituted di(C₁-C₄alkyl)amino; and

[0064] Z is oxygen.

[0065] Preferably the aqueous phase is from 25 to 95% more preferablyfrom 40 to 80% and most preferred from 45 to 75% by weight, based on thetotal mixture.

[0066] The total mixture contains water, at least one monomer, the abovementioned regulator and initiator and in many cases at least onesurfactant and/or a organic solvent.

[0067] Optionally other water miscible solvents may be present usuallyless than 10% by weight based on the water content. Exemplary cosolventsuseful in the present invention may be selected from the groupconsisting of aliphatic alcohols, glycols, ethers, glycol ethers,pyrrolidines, N-alkyl pyrrolidinones, N-alkyl pyrrolidones, polyethyleneglycols, polypropylene glycols, amides, carboxylic acids and saltsthereof, esters, organosulfides, sulfoxides, sulfones, alcoholderivatives, hydroxyether derivatives such as butyl carbitol orcellosolve, amino alcohols, ketones, and the like, as well asderivatives thereof and mixtures thereof. Specific examples includemethanol, ethanol, propanol, dioxane, ethylene glycol, propylene glycol,diethylene glycol, glycerol, dipropylene glycol, tetrahydrofuran, andother water-soluble or water-miscible materials, and mixtures thereof.

[0068] Preferred are water, water alcohol mixtures, water ethyleneglycol or propylene glycol mixtures, water acetone, watertetrahydrofurane, or water dimethylformamide mixtures.

[0069] Preferably the solids content of the resulting polymer dispersionis between 15-60% by weight.

[0070] Preferably the nitroxyl radical of component a) is present in anamount of from 0.001 mol-% to 20 mol-%, based on the monomer or monomermixture.

[0071] In case of monomer mixtures an average molecular weight iscalculated.

[0072] Preferably the free radical initiator is present in an amount offrom 0.01 mol-% to 20 mol-%, more preferably from 0.1 mol-% to 10 mol-%and most preferably from 0.2 mol-% to 5 mol-%, based on the monomer ormonomer mixture.

[0073] Preferably the molar ratio of free radical initiator to stablefree nitroxyl radical is from 20:1 to 1:2, more preferably from 10:1 to1:2.

[0074] The temperature for polymerization is preferably from 60° C. to180° C., more preferably from 80° C. to 140° C. and most preferably from80° C. to 110° C.

[0075] The pressure during the reaction depends on the temperatureapplied and is preferably between 0.1 bar and 20 bar, more preferablybetween 1 and 10 bar.

[0076] The reaction mixture may also contain a buffer to adjust andmaintain the pH value, preferably between 4.5 and 9. Phosphate or citricacid buffers are preferred.

[0077] The process is particularly useful for the preparation of blockcopolymers.

[0078] Block copolymers are, for example, block copolymers ofpolystyrene and polyacrylate (e.g., poly(styrene-co-acrylate) orpoly(styrene-co-acrylate-co-styrene). They are usefulI as adhesives oras compatibilizers for polymer blends or as polymer toughening agents.Poly(methylmethacrylate-co-acrylate) diblock copolymers orpoly(methylacrylate-co-acrylate-co-methacrylate) triblock copolymers)are useful as dispersing agents for coating systeme, as coatingadditives (e.g. Theological agents, compatibilizers, reactive diluents)or as resin component in coatings (e.g. high solid paints) Blockcopolymers of styrene, (meth)acrylates and/or acrylonitrile are usefulfor plastics, elastomers and adhesives.

[0079] Furthermore, block copolymers of this invention, wherein theblocks alternate between polar monomers and non-polar monomers, areuseful in many applications as amphiphilic surfactants or dispersantsfor preparing highly uniform polymer blends.

[0080] Particularly, emulsion polymerization is especially suitable tobuild-up polymer particles with specific morphology. For example,core/shell structures can be achieved by consecutively changing monomersduring polymerization. These special particles are useful for improvingimpact resistance of plastics. Oftenly, these core/shell structures arepolymer blends of at least two types of polymers which are formed withinthe polymer particle during emulsion polymerization. By applyingcontrolled free radical polymerization during consecutive monomer feed,block copolymers are formed which improve the compatibilizing effect ofthe different polymers within the polymer particle. Furthermore,core/shell structures can be synthesized by grafting a different monomerduring emulsion polymerization on polymer particles containingunsaturations, e.g. butadiene (co-)polymers. Applying controlled freeradical polymerization within this grafting process, graft polymers withuniform graft arm lengths and even new graft polymers are accessible.

[0081] Consequently the formation of block and graft polymers is asubject of the present invention.

[0082] The (co)polymers of the present invention may have a numberaverage molecular weight from 1 000 to 400 000 g/mol, preferably from 2000 to 250 000 g/mol and, more preferably, from 2 000 to 200 000 g/mol.The number average molecular weight may be determined by size exclusionchromatography (SEC), matrix assisted laser desorption/ionization massspectrometry (MALDI-MS) or, if the initiator carries a group which canbe easily distinguished from the monomer(s), by NMR spectroscopy orother conventional methods.

[0083] The polymers or copolymers of the present invention havepreferably a polydispersity of from 1.1 to 2, more preferably of from1.2 to 1.8.

[0084] The average particle diameter of the dispersed polymer particlesis preferably from 25 nm to 1000 nm, more preferably 200 nm to 700 nm.Particle size may for example be measured by a high speed centrifuge orby photon correlation spectroscopy.

[0085] The particle size distribution may be monomodal or bimodal.

[0086] The process of emulsion polymerization per se is known and forexample described in WO 99/00426 or in WO00/50480. It may be carried outas a batch process or in a continuous or semi continuous process.

[0087] The initiator and/or regulator may for example be added at thebeginning of the reaction, however it is also possible to add one or theother in portions or continuously at the beginning and during thereaction.

[0088] Suitable surfactants or surface active compounds which may beadded are known in the art. The amounts typically used range from 0.01%by weight to 10% by weight, based on the monomer or monomers.

[0089] Suitable surface active compounds are protective colloids such aspolyvinylalcohols, starch, cellulose derivatives or copolymerscontaining vinylpyrrolidone. Further examples are given in “Houben-Weyl,Methoden der Organischen Chemie, Band XIV/1, Makromolekulare Stoffe, G.Thieme Verlag Stuttgart 1961, 411-420”.

[0090] Typical surfactants useful in the present invention are ofnonionic, cationic or anionic type.

[0091] Examples for anionic surfactants are alkali and ammonium salts ofC₁₂-C₁₈alkylsulfonic acid, dialkyl esters of succinic acid or sulfuricacid halfesters of ethoxylated alkanoles. These compounds are known forexample from U.S. Pat. No. 4,269,749 and largely items of commerce, suchas under the trade name Dowfax® 2A1 (Dow Chemical Company).

[0092] Nonionic surfactants are for example aliphatic or araliphaticcompounds such as ethoxylated phenols (mon, di, tri) with anethoxylation degree of 3 to 50 and alkyl groups in the range from C₄-C₉,ethoxylated long chain alcohols or polyethyleneoxide/polypropyleneoxideblock copolymers.

[0093] The emulsion polymerization may be carried out as seed freeprocess or according to a seed-latex process which seed latex may alsobe prepared in situ. Such processes are known and for example describedin EP-A-614 922 or in EP-A-567 812.

[0094] The present invention also encompasses in the synthesis novelblock, multi-block, star, gradient, random, hyperbranched and dendriticcopolymers, as well as graft copolymers.

[0095] The polymers prepared by the present invention are useful forfollowing applications:

[0096] adhesives, detergents, dispersants, emulsifiers, surfactants,defoamers, adhesion promoters, corrosion inhibitors, viscosityimprovers, lubricants, rheology modifiers, thickeners, crosslinkers,paper treatment, water treatment, electronic materials, paints,coatings, photography, ink materials, imaging materials,superabsorbants, cosmetics, hair products, preservatives, biocidematerials or modifiers for asphalt, leather, textiles, ceramics andwood.

[0097] Because the present polymerizaton is a “living” polymerization,it can be started and stopped practically at will. Furthermore, thepolymer product retains the functional alkoxyamine group allowing acontinuation of the polymerization in a living matter. Thus, in oneembodiment of this invention, once the first monomer is consumed in theinitial polymerizing step a second monomer can then be added to form asecond block on the growing polymer chain in a second polymerizationstep. Therefore it is possible to carry out additional polymerizationswith the same or different monomer(s) to prepare multi-block copolymers.Furthermore, since this is a radical polymerization, blocks can beprepared in essentially any order. One is not necessarily restricted topreparing block copolymers where the sequential polymerizing steps mustflow from the least stabilized polymer intermediate to the moststabilized polymer intermediate, such as is the case in ionicpolymerization. Thus it is possible to prepare a multi-block copolymerin which a polyacrylonitrile or a poly(meth)acrylate block is preparedfirst, then a styrene or butadiene block is attached thereto, and so on.

[0098] The following examples illustrate the invention.

[0099] General

[0100] Polymers are characterized by gel-permeation-chromatography(GPC), with a Hewlett Packard HP 1090 LC, column PSS 1, length 60 cm,elution with tetrahydrofurane (THF), rate 1 m/min, concentration 10 mgpolymer in 1 ml THF, Calibration with styrene. Polydispersity iscalculated from Mn (g/mol) and Mw (in g/mol) as PD=Mw/Mn.

[0101] Log p is calculated using the following program:

[0102] LOGKOWNT program (Windows NT console application)

[0103] Syracuse Research Corporation

[0104] 6225 Running Ridge Road

[0105] North Syracuse

[0106] N.Y. 13212

[0107] Nitroxyls

[0108] Nitroxyls are prepared according to GB 2335190 and GB 2342649.

[0109] Initiators

[0110] Initiators used are commercial products of Aldrich and WAKOChemicals.

[0111] Emulsion Polymerization

[0112] Examples 1-10 are carried out using 40 g styrene, 320 g water and1.8 g sodium dodecylsulfate. The mixture is degassed with argon.

[0113] For examples 1-10 the initiator is either 0.3322 g WAKO VA086(commercial azo-initiator) or 0.3115 g potassium peroxodisulfate (KPS),both dissolved in additional 20 g water and degassed with argon.

[0114] The nitroxyl radicals are added as indicated in Table 1 eitherdissolved in additional 20 g water or in additional 20 g styrenedegassed with argon.

[0115] Polymerization at 100° C.

[0116] Polymerization at 100° C. is carried out in a three neck flaskwith reflux condenser, dropping funnel with nitrogen balloon andstirrer.

[0117] The regulator solution and the styrene water mixture are filledinto the three neck flask under nitrogen atmosphere under stirring with320 rounds per minute. The mixture is heated to 100° C. in 45 minutesand the initiator solution is dropwise added within 2 minutes. Thereaction mixture is kept at 100° C. for 23 hours and stirred with 320rounds per minute. After cooling down the reaction mixture and dryingthe residue under vacuum the yield is determined gravimetrically.Polymer characterization is carried out from a solution of the polymerin tetrahydrofurane.

[0118] Polymerization at 120° C.

[0119] Polymerization at 120° C. is carried out in a double wall threeneck flask with reflux condenser, pressuring and vacuum unit andstirrer.

[0120] Polymerization is carried out as described above with thefollowing differences:

[0121] stirring speed: 600 rounds per minute; nitrogen pressure: 5 bar,temperature: 120° C.; and reaction time 9 hours.

[0122] The polymerization runs are given in Table 1. TABLE 1 AmountTempera- Nitroxyl ture/Time No. Initiator Nitroxyl-Radical [g] log p [°C./h] B1 KPS

0.6859 2.6 100/23 dissolved in styrene B2 KPS

0.6226 3.0 100/23 dissolved in Styrene B3 KPS

0.9607 2.2 100/23 dissolved in water B4 VA086

0.9274 2.6 120/9 dissolved in styrene B5 VA086

0.6234 3.0 120/9 dissolved in styrene B6 VA086

0.5932 3.0 120/9 dissolved in styrene B7 VA086

0.5187 2.2 120/9 dissolved in water B8 VA086

0.2963 3.0 100/23 dissolved in styrene B9 KPS

0.3078 3.0 100/23 dissolved in styrene B10 VA086

0.2278 3.0 100/23 dissolved in styrene

[0123] The results are given in Table 2. TABLE 2 Mn Mw Yield No. [g/mol][g/mol] PD [1%] B1 8.800 9.700 1, 1 48 B2 10.800 13.000 1.2 64 B3 23.20027.300 1.2 80 B4 3.700 4.500 1.2 21 B5 7.500 9.100 1.2 32 B6 6.300 7.7001.2 22 B7 19.000 25.000 1.3 57 B8 18.000 22.100 1.2 34 B9 15.000 17.7001.2 62 B10 33.000 41.400 1.3 44

EXAMPLES B11 AND B12 Variation of Initiators

[0124] The emulsion polymerizations are performed as described in thegeneral procedure but by varying the type and amount of initiators.Furthermore, the amount of nitroxyl compound No. 102 is varied. Theexamples are summarized in Table 3. TABLE 3 Amount Nitroxyl Amount ofInitiator Compound No. 102 No. Type of Initiator [g] [g] B11 WAKO V-500.3151 0.2965 B12 tert-BuOOH 0.1176 0.4141

[0125] All polymerizations are carried out at 100° C. for 23 h. Theresults are presented in Table 4. TABLE 4 Mn Mw Yield No. [g/mol][g/mol] PD [%] B11 14200 16000 1.1 30 B12 1.500 1.700 1.1 5

[0126] Comparative polymerization runs are given in Table 5 and 6. TABLE5 Amount Temperature/ Nitroxyl Time No. Initiator Nitroxyl-Radical [g]log p [° C./h] V1 VA086 — — — 100/23 V2 KPS — — —  85/23 V3 VA086

0.9620 7.9 120/9 dissolved in styrene V4 VA086

0.9594 7.9 100/23 dissolved in styrene V5 KPS

0.9658 7.9 100/23 dissolved in styrene

[0127] The results of the comparative examples are presented in Table 6.TABLE 6 Mn Mw Yield No. [g/mol] [g/mol] PD [%] V1 253.000 943.000 3.7100 V2 95.000 397.000 4.2 100 V3 7.000 158.000 23 13 V4 383.0001.046.000   2.7 77 V5 49.000 538.000 11 85

[0128] From the comparative experiments it becomes apparent that PDexceeds 2 significantly, indicating that essentially no control of thepolymerization exists.

EXAMPLE B13 Emulsion Polymerization of n-butylacrylate

[0129] Following formulation is emulsion polymerized at 100° C. for 23 has described in the general procedure:

[0130] 60 g n-butylacrylate

[0131] 344 g water

[0132] 1.8 g sodium dodecylsulfate

[0133] 0.2537 g potassium peroxodisulfate (KPS)

[0134] 0.5099 g of compound No. 102 Yield: 6% GPC-results: Mn: 820 g/molMw: 930 g/mol PD: 1.1

EXAMPLE B14 Emulsion Co-Polymerization of n-butylacrylate and Zonvl®TA-M

[0135] Following formulation is emulsion polymerized at 120° C. for 9 has described in the general procedure:

[0136] 40 g n-butylacrylate

[0137] 20 g Zonyl TA-M (commercial available fluoro acrylatecomposition; CAS RN 132324-93-7)

[0138] 340 g water

[0139] 1.8 g sodium dodecylsulfate

[0140] 0.1080 g VA086

[0141] 0.1587 g of compound No. 103 Yield: 34% GPC-results: Mn: 15.200g/mol Mw: 17.500 g/mol PD: 1.2

EXAMPLE B15 Emulsion Co-Polymerization of Styrene and Acrylonitrile

[0142] Following formulation is emulsion polymerized at 100° C. for 23 has described in the general procedure:

[0143] 60 g styrene

[0144] 20 g acrylonitril

[0145] 320 g water

[0146] 1.8 g sodium dodecylsulfate

[0147] 0.5169 g potassium peroxodisulfate (KPS)

[0148] 0.6413 g of compound No. 102

[0149] Acrylonitril is added 30 min. after addition of the initiator.Yield: 52% GPC-results: Mn: 17.300 g/mol Mw: 24.500 g/mol PD: 1.4

EXAMPLE B16 Re-Initiation of PS-Macroinitiator with Styrene

[0150] 2.5 g of the product of example B5 are dissolved in 25 mlstyrene. The solution is purged with Argon and heated for 24 h at 130°C. The product is precipitated in methanol and dried. Yield: 90%GPC-results: Mn: 47.200 g/mol Mw: 60.000 g/mol PD: 1.3

EXAMPLE B17 Synthesis of Polystyrene-Block-n-Butylacrylate:

[0151] 5 g of the product of example 85 are dissolved in 25 gn-butylacrylate. The solution is purged with Argon and heated for 24 hat 145° C. The product is precipitated in methanol and dried. Yield: 14%GPC-results: Mn: 13.000 g/mol Mw: 16.500 g/mol PD: 1.3

EXAMPLE B18 Re-Initiation of PS-Macroinitiator with Styrene

[0152] 5 g of the product of example B9 are dissolved in 50 ml styrene.The solution is purged with Argon and heated for 24 h at 130° C. Theproduct is precipitated in methanol and dried. Yield: 77% GPC-results:Mn: 69.000 g/mol Mw: 99.400 g/mol PD: 1.4

EXAMPLE B19 Synthesis of Polystyrene-Block-n-Butylacrylate

[0153] 5 g of the product of example B9 are dissolved in 25 gn-butylacrylate. The solution is purged with Argon and heated for 24 hat 145° C. The product is precipitated in methanol and dried. Yield: 38%GPC-results: Mn: 24,500 g/mol Mw: 34,600 g/mol PD: 1, 4

EXAMPLE B20 Synthesis of Polystyrene-Block-n-Butylacrylate in Emulsion(One Pot)

[0154] Following formulation is emulsion polymerized at 100° C. for 36 has described in the general procedure:

[0155] 60 g styrene

[0156] 340 g water

[0157] 1.8 g sodium dodecylsulfate

[0158] 0.3122 g potassium peroxodisulfate (KPS)

[0159] 0.6211 g of compound No. 102

[0160] After 36 h, a sample is taken and the molecular weightdistribution is characterized: GPC-results: Mn: 17.900 g/mol Mw: 23.600g/mol PD: 1, 3

[0161] After adding 60 g n-butylacrylate drop wise within 15 min, theemulsion polymerization is continued for additional 60 hours at 100° C.The product is worked-up according to the general procedure describedbefore. Overall conversion: 63% GPC-results: Mn: 25.000 g/mol Mw: 32,400g/mol PD: 1, 3

[0162] The block copolymer is analyzed by ¹H-NMR (CDCI₃-solution), whichrevealed following co-monomer composition: First block: 100 mol %styrene Second block:  69 mol % n-butylacrylate, 31 mol % styrene.

1. A process for preparing an oligomer, a cooligomer, a polymer or acopolymer (block or random) by free radical polymerization in aqueousdispersion of at least one ethylenically unsaturated monomer oroligomer, which comprises forming an aqueous dispersion having themonomer in the disperse phase and (co)polymerizing the monomer ormonomers/oligomers at elevated temperature in the presence of a) atleast one stable free nitroxyl radical which has a log p (octanol/water)of between −0.5 and 7.5 and which is selected from the group consistingof a compound of formula (A), (B), (C), (D), (E), (F), (G), (H) or (I)

 wherein R is hydrogen, C₁-C₁₈alkyl which is uninterrupted orinterrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl,a monovalent radical of an aliphatic carboxylic acid having 2 to 18carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbonatoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atomsor of an aromatic carboxylic acid having 7 to 15 carbon atoms; R₁₀₁ isC₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoylor benzoyl; R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenylunsubstituted or substituted by a cyano, carbonyl or carbamide group, oris glycidyl, a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Zor —CONH—Z wherein Z is hydrogen, methyl or phenyl; G₅ is hydrogen andG₅ is hydrogen or C₁-C₄alkyl, and G₁ and G₃ are methyl and G₂ and G₄ areethyl or propyl or G₁ and G₂ are methyl and G₃ and G₄ are ethyl orpropyl; R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinylwhich are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkylwhich is interrupted by at least one O atom and/or NR₅ group,C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R₄ togetherwith the linking carbon atom form a C₃-C₁₂cycloalkyl radical; R₅, R₆ andR₇ independently are hydrogen, C₁-C₁₈alkyl or C₆-C₁₀aryl; R₈ ishydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl; C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by one or more OH,halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by atleast one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl,C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl, —O—C₁-C₁₈alkyl or—COOC₁-C₁₈alkyl; and R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen,phenyl or C₁-C₁₈alkyl; and b) a free radical initiator.
 2. A processaccording to claim 1, wherein in formula A, B and C R is hydrogen,C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, a monovalent radical of analiphatic, carboxylic acid; R₁₀₁ is C₁-C₁₂alkyl, C₇C₈aralkyl,C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl; R₁₀₂ is C₁-C₁₈alkyl, glycidyl,a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z, wherein Zis hydrogen, methyl or phenyl.
 3. A process according to claim 1,wherein in formula (D), (E), (F), (G), (H) and (I) at least two of R₁,R₂, R₃ and R₄ are ethyl, propyl or butyl and the remaining are methyl;or R₁ and R₂ or R₃ and R₄ together with the linking carbon atom form aC₅-C₆cycloalkyl radical and one of the remaining substituents is ethyl,propyl or butyl.
 4. A process according to claim 1, wherein the freeradical initiator of component b)-is a bis-azo compound, a peroxide or ahydroperoxide.
 5. A process according to claim 1, wherein the nitroxylradical of component a) is present in an amount of from 0.001 mol-% to20 mol-%, based on the monomer or monomer mixture.
 6. A processaccording to claim 1, wherein the free radical initiator is present inan amount of 0.01 mol-% to 20 mol-%, based on the monomer or monomermixture.
 7. A process according to claim 1, wherein the molar ratio offree radical initiator to stable free nitroxyl radical is from 20:1 to1:2.
 8. A process according to claim 1, wherein the temperature forpolymerization is from 60° C. to 180° C.
 9. A process according to claim1, wherein the pressure during the reaction is between 0.1 bar and 20bar.
 10. A process according to claim 1, wherein the ethylenicallyunsaturated monomer is selected from the group consisting of styrene,substituted styrene, conjugated dienes, acrolein, vinyl acetate,vinylpyrrolidone, vinylimidazole, maleic anhydride, (alkyl)acrylicacidanhydrides, (alkyl)acrylic esters, (meth)acrylonitriles,(alkyl)acrylamides.
 11. A process according to claim 10, wherein theethylenically unsaturated monomer is selected from the group consistingof styrene, acrylic acid ester, acrylamide, acrylnitrile, methacrylicacid ester, methacrylamide, methacrylnitrile.
 12. A process according toclaim 1, wherein the polymer formed is a block copolymer or a graftcopolymer.